The aim of this research is to reconstitute DNA replication in vitro. We have isolated twenty or more proteins which are involved in DNA synthesis using either single stranded or double stranded DNA as a template. This system will then be the best possible one for the study of the mechanism of inhibition by drugs like ara CPT nalidixic acid and daunomycin. We are trying to find out if there are any specific drug: protein interactions. We have found that a crude protein fraction which can carry out DNA synthesis exhibits allosteric behavior with respect to different concentrations of ATP. We are also trying to find out if some drugs behave as allosteric modulators.